Copper-zirconia catalyst and method of use and manufacture

ABSTRACT

Catalysts and methods for their manufacture and use for the dehydrogenation of alcohols are disclosed. The catalysts and methods utilize a highly dispersible alumina, for example, boehmite or pseudoboehmite, to form catalysts that exhibit high dehydrogenation activities. Specifically, the catalysts include Cu that is highly dispersed by reaction of an alumina formed by peptizing of boehmite or pseudoboehmite and precursors of ZrO 2 , ZnO and CuO.

TECHNICAL FIELD

The present invention relates to catalysts, methods for preparingcatalysts and methods using the catalyst to produce esters, for example,for converting ethanol to ethyl acetate.

BACKGROUND

Dehydrogenation is a chemical reaction that involves the elimination ofhydrogen (H₂) and is used in large scale industrial processes or smallerscale laboratory procedures. Copper is a known catalyst fordehydrogenation reactions, however, the activity and selectivity of thecatalyst can be significantly enhanced by the correct use of promotersas well as the correct method of preparation of the catalyst. Zinc oxide(ZnO), zirconium oxide (ZrO₂) and aluminum oxide (Al₂O₃) have been usedas components with various Cu-containing catalysts. In general, suchCu-containing catalysts are made using ZnO, ZrO₂ and Al₂O₃ precursors,such as soluble salts of the components such as copper nitrate, zincnitrate, zirconyl nitrate, and aluminum nitrate and their simultaneousprecipitation with a base such as sodium carbonate or bicarbonate.

Dehydrogenation can be used in reactions with alcohols. For example,dehydrogenation may be used to dehydrogenate methanol to giveformaldehyde, ethanol to give acetaldehyde, 1-propanol to givepropionaldehyde, isopropanol to give acetone, 1-butanol to givebutyraldehyde, 2-butanol to give methyl ethyl ketone, isobutanol to giveisobutyraldehyde, and also for dehydrogenating the isomeric primary andsecondary pentanols, hexanols, heptanols, octanols, nonanols, decanols,undecanols and dodecanols to give the corresponding aldehydes andketones respectively.

One such product formed from the dehydrogenation of ethanol includesethyl acetate, which is commonly used as a solvent. The synthesis ofethyl acetate typically utilizes reactions between ethanol and aceticacid or the dehydrogenation of ethanol. Recently, interest insynthesizing ethyl acetate by dehydrogenating ethanol has increasedbecause surplus ethanol feedstock can be used. Examples of catalysts andmethods known in the art for forming ethyl acetate include the catalystdescribed in U.S. Pat. No. 7,091,155 B2 and the catalysts and methodsdisclosed in Chinese patent ZL Patent No. 92100590.3.

It would be desirable to provide dehydrogenation catalysts, methods fortheir manufacture and methods of use which exhibit higher catalyticactivity than existing catalysts.

SUMMARY

A first aspect of the present invention pertains to a catalystcomprising CuO, ZnO, ZrO₂ and Al₂O₃, wherein the Al₂O₃ in the catalystis derived from a highly dispersible alumina, instead of aluminumnitrate. As used herein, the term “dispersible alumina” refers to theamount of alumina that becomes colloidal at a certain pH, which istypically in the acid range, a process that is referred to as acidpeptizing. Acid peptizing results in the formation of particles that areless than 1 micron (μm). Examples of dispersible alumina include aluminahaving 40% or greater dispersibility in water after peptizing at a pH of2 to 5. Other examples of alumina having 50% or greater dispersibility,60% or greater dispersibility, 70% or greater dispersibility, 80% orgreater dispersibility, or 90% or greater dispersibility in water afterpeptizing at a pH of 2 to 5 are included in this definition ofdispersible alumina. As used herein, the percent dispersibility ofalumina refers to the percentage of alumina that is less than 1 micronin size in the acidic solution after peptizing at a pH from about 2 toabout 5. Non-limiting examples of aluminas that are dispersible includeboehmite or pseudo-boehmite aluminas.

One or more embodiments of the present invention pertain to adehydrogenation catalyst comprising about 10 to about 75 wt % CuO, about5 to about 50 weight % ZnO, about 1 to about 30 weight % ZrO₂, and about5 to about 40 weight % alumina prepared by peptizing dispersible aluminawith a dispersibility of at least about 50% or greater and reacting thealumina with precursors of CuO, ZnO, and ZrO₂. The dehydrogenationcatalyst of one or more embodiments may exhibit an XRD patterncontaining boehmitic peaks at 2 theta values of about 14.2° and 28.1°.

In one variant, the dispersible alumina may have a dispersibility of atleast 70% or greater or 90% or greater. The dispersible alumina may beselected from boehmite, pseudoboehmite, and mixtures thereof. In one ormore embodiments, at least a portion of the dispersible alumina may bereplaced with nondispersible alumina. For example, up to 99% by weightof the dispersible alumina may be replaced with nondispersible alumina.The non-dispersible alumina may be selected from γ-alumina, η-alumina,χ-alumina, other transitional aluminas, boehmite, pseudoboehmite,gibbsite, bayerite, and mixtures thereof.

A second aspect of the present invention pertains to a process ofpreparing the dehydrogenation catalysts disclosed herein. In one or moreembodiments, the process of preparing the dehydrogenation catalystsincludes peptizing a highly dispersible alumina to form a peptizedalumina and reacting the peptized alumina with precursors of ZrO₂, ZnOand CuO.

In one or more embodiments, the process includes forming the peptizedalumina by forming a slurry by peptizing a dispersible alumina in anacid at a pH between 2 and 5 and a temperature of about 20° C. to 30° C.In a specific embodiment, the process may include peptizing adispersible alumina at a pH of about 3 and a temperature of about 25° C.The dispersible alumina of one or more embodiments may be replaced withnon-dispersible alumina. In a specific variant, up to 99% by weight ofthe dispersible alumina may be replaced with nondispersible alumina.

The process may include forming a ZrO₂ precursor by forming a slurry ofzirconyl nitrate and water in a separate vessel from the peptizedalumina. The slurry of zirconyl nitrate is then mixed with the slurryformed above by peptizing a dispersible alumina to form a mixed slurryor a new slurry. In one or more embodiments, the slurry of zirconylnitrate and water is formed at a pH of less than about 1.5 and atemperature in the range of about 20° C. to 30° C. In one variant, theslurry of zirconyl nitrate and water may be formed at a pH of about 1.0and a temperature of about 25° C. After mixing the two slurries to forma mixed slurry, the process may also include maintaining the pH of themixed slurry at less than about 1.5 and a temperature in the range ofabout of about 20° C. to 30° C. In a specific embodiment, the processincludes maintaining the mixed slurry at a pH of about 1.0 at atemperature of about 25° C. As used herein, the mixed slurry may bereferred to as a new slurry or a first reaction product.

The process may include forming a Cu and Zn precursor by forming asolution of copper nitrate and zinc nitrate and mixing the solution withthe mixed slurry formed above. As used herein, the copper nitrate andzinc nitrate solution may be referred to as a second reaction product.In one or more embodiments, the copper nitrate and zinc nitrate solutionis formed at a pH of less than about 1.5 and at a temperature in therange of about 30° C. to 50° C. In one variant, the process includesforming a solution of copper nitrate and zinc nitrate at a pH of about1.0 at a temperature of about 40° C. In one or more embodiments, theprocess includes mixing the copper nitrate and zinc nitrate solution(second reaction product) with the mixed slurry (or first reactionproduct). During mixing, the process may include maintaining the pH atless than about 1.5, while raising the temperature to a range of about30° C. to 50° C. to create an acidic slurry containing copper nitrate,zinc nitrate, zirconyl nitrate, and alumina. In one variant, the step ofmixing the copper nitrate and zinc nitrate solution with the mixedslurry includes maintaining the pH at about 1.0, while the temperatureis raised or increased to about 40° C.

In one or more embodiments, the process includes adding a basic solutionand the acidic slurry formed above to a vessel containing a heel ofwater. In one variant, the process includes forming a basic solution ofsodium carbonate or sodium bicarbonate at a temperature in the range ofabout 30° C. to 50° C. in one vessel and forming a heel of water in aseparate vessel at a temperature in the range of about 30° C. to 50° C.The solution of sodium carbonate or sodium bicarbonate and/or the heelof water may be formed at a temperature of about 40° C. In one or moreembodiments, the process includes adding the basic solution and theacidic slurry prepared above to the vessel containing the heel of waterso that a precipitation reaction occurs at a pH of about 6 to 7 and at atemperature in the range of about 30° C. to 50° C. to provide aprecipitate slurry. The acidic slurry and the basic solution may beadded to the heel of water so that the precipitation reaction may occurat a pH of about 6.5 at a temperature of about 40° C.

The process may also include aging the precipitate slurry formed fromthe precipitation reaction for a time in the range of about 15 minutesto 15 hours at a temperature in the range of about 30° C. to 70° C. Inone variant, the precipitate slurry may be aged for about 2 hours at atemperature of about 60° C. The precipitate slurry may be filtered andwashed to provide or form a filter cake. The filter cake may be dried toform a dry filter cake or powder and calcined to decompose carbonates tooxides, in accordance with one or more embodiments of the process.

A third aspect of the present invention pertains to a method fordehydrogenating alcohol, which may include ethanol. In one or moreembodiments, the method includes contacting an alcohol-containing streamwith a dehydrogenation catalyst as described herein and converting thealcohol to ester, which may comprise ethyl acetate. In one variant,prior to contacting the alcohol-containing stream, the method includesreducing the dehydrogenation catalyst in a stream containing hydrogen.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an XRD pattern of the copper-zirconia catalyst preparedaccording to Example 1.

DETAILED DESCRIPTION

Before describing several exemplary embodiments of the invention, it isto be understood that the invention is not limited to the details ofconstruction or process steps set forth in the following description.The invention is capable of other embodiments and of being practiced orbeing carried out in various ways.

A first aspect of the present invention pertains to a dehydrogenationcatalyst comprising Cu, ZnO, ZrO₂ and Al₂O₃. In one embodiment, thecatalyst exhibits increased dehydrogenation activity compared toconventional catalysts used in dehydrogenation reactions. In one or moreembodiments, the catalyst comprises Cu, ZnO, ZrO₂ and Al₂O₃ and thecatalyst can be prepared by using highly dispersible alumina. Inspecific embodiments, the Cu of the catalyst is highly dispersed byreaction of precursors of ZrO₂, ZnO and CuO and an alumina formed bypeptizing of boehmite or pseudoboehmite. In one embodiment, adehydrogenation catalyst comprises Cu, ZnO, ZrO₂ and Al₂O₃, wherein theCuO is present in an amount of about 10% to about 75% by weight of thecatalyst. The catalyst may be prepared by reaction of an alumina formedby peptizing of boehmite or pseudoboehmite and precursors of ZrO₂, ZnOand CuO, wherein the alumina has a dispersibility of at least about 50%.In other specific embodiments, the alumina may have a dispersibility ofat least about 70% and at least about 90%.

In one or more specific embodiments, the Cu has a surface area exceeding15 m²/g of the catalyst. In an even more specific embodiment, the Cu hasa surface area exceeding 20 m²/g of the catalyst. The catalyst of one ormore embodiments may include Cu with a surface area exceeding 25 m²/g ofthe catalyst. In one or more embodiment, CuO is present in the catalystin an amount in the range of from about 30% to about 70% by weight ofthe catalyst. In a specific embodiment, CuO is present in an amount inthe range from about 40% by weight to about 60% by weight. In a morespecific embodiment, CuO is present in an amount in the range from about45% to about 55% by weight. In one or more embodiments, ZnO, ZrO₂ andAl₂O₃ comprise the remaining amount of the catalyst, or morespecifically, from the range of about 70% to about 30% by weight of thecatalyst, and more specifically in the range of about 60% to about 40%by weight of the catalyst. In one or more specific embodiments, ZnO maybe present in an amount in the range from about 5 weight % to about 50weight %, ZrO₂ may be present in an amount in the range from about 1weight % to about 30 weight % and Al₂O₃ may be present in an amount inthe range from about 5 weight % to about 40 weight %.

The catalyst according to one or more embodiments may have a BET totalsurface area of greater than about 140 m²/g. The catalyst may exhibit anXRD pattern containing boehmitic peaks at 2 theta values of about 14.2°and 28.1°.

The alumina utilized in the catalysts described herein is characterizedas peptized until the desired dispersibility or a “dispersible alumina,”as defined above, is achieved. According to one or more specificembodiments, the use of a highly dispersible alumina allows more of thesurface area of the Cu to be exposed for reaction and thus provides ahigher catalytic activity. In one or more embodiments, the peptizedalumina has a particle size of 1 μm or less. In one more embodiments,the alumina has 40% or greater dispersibility in water after peptizingat a pH of 2 to 5. In other words, the percentage of alumina having aparticle size of 1 μm or less in water after peptizing at a pH of 2 to 5is at least 40%. In one more embodiments, the alumina has 50% or greaterdispersibility in water after peptizing at a pH of 2 to 5. In a morespecific embodiment, the alumina has 80% or greater dispersibility inwater after peptizing at a pH of 2 to 5. Other suitable alumina may have90% or greater dispersibility in water after peptizing at a pH of 2 to5. In one or more alternative embodiments, non-dispersible alumina maybe used in combination with dispersible alumina. In such embodiments,the non-dispersible alumina is milled into a fine powder before use.

The catalyst includes Al₂O₃ which may be formed or derived fromboehmite, pseudoboehmite and combinations thereof. Suitable boehmite andpseudoboehmites have 70% or greater dispersibility in water afterpeptizing at a pH of 2 to 5. For example, suitable aluminas areavailable from Sasol North America Inc. of Houston, Tex., under thetrademarks Catapal®, Pural®, Dispersal®, and Dispal®. Examples ofaluminas that may be utilized in the catalysts described herein includealuminas available under the trade names Catapal A, B, Cl, and D andPural SB. A specific example of a suitable alumina is available underthe trade name CATAPAL D and has a particle size d₅₀ of about 40 μm. Thealumina available under the trade name CATAPAL D also has a BET surfacearea of 220 m²/g and a pore volume of about 0.55 ml/g after activationat 550° C. for 3 hours.

As will be understood, other sources of alumina can be used and includesuch diverse materials as aluminum nitrate. Some dispersible aluminasources are thought to be unsuitable for industrial scale applicationsbecause of their tendency to gel or become solid under normal operatingconditions in an industrial or large-scale setting. Accordingly, manyknown catalysts and methods of making and using such catalysts utilizedaluminum nitrate as an alumina source. Modifying these known aluminasources, for example, aluminum nitrate and aluminum powders, wereconsidered, however, none of these yielded the high Cu dispersion andenhanced catalytic activity desired. The dispersible alumina of thepresent invention is selected, despite the many issues regarding itsuse, and modified by peptizing to achieve the high Cu dispersion.Specifically, as stated above, the Cu of one or more catalysts describedherein is highly dispersed by the reaction of an alumina derived bypeptizing of boehmite or pseudoboehmite and precursors of ZrO₂, ZnO andCuO.

In one or more embodiments, at least a portion of the dispersiblealumina in the catalyst may be replaced with nondispersible alumina.Suitable nondispersible alumina include γ-alumina, η-alumina, χ-alumina,other transitional aluminas, boehmite, pseudoboehmite, gibbsite,bayerite, and mixtures thereof.

The catalyst according to one or more embodiments includes ZrO₂, ZnO andCuO which are formed from various precursors. A suitable ZrO₂ precursorincludes zirconyl nitrate though other known precursors may be utilized.When zirconyl nitrate is used as the zirconia precursor, the ZrO₂precursor is provided by forming a slurry of zirconyl nitrate and water.In such embodiments, it is desirable to maintain the reaction mixture orthe zirconyl nitrate and water slurry at a pH of less than about 2, andin specific embodiments at a pH of less than about 1.5 or 1. In one ormore specific embodiments, the reaction mixture or the zirconyl nitrateslurry is maintained at a pH of about 1. In one or more embodiments, thereaction mixture is maintained or has a temperature in the range fromabout 20° C. to about 30° C. In one or more embodiments, the temperatureof the zirconyl nitrate slurry may be maintained at a temperature ofabout 25° C.

A suitable CuO precursor includes copper nitrate. A suitable ZnOprecursor includes zinc nitrate. In one or more embodiments, thecatalyst is formed by first reacting a ZrO₂ precursor with the peptizedalumina to provide a first reaction product, a mixed slurry or a newslurry. A second reaction is then performed in which the CuO and ZnOprecursors are reacted in a separate vessel to form or provide a secondreaction product. The first reaction product and second reaction productare then subsequently mixed together.

A second aspect of the present invention pertains to a method ofpreparing a catalyst as described herein. In one or more embodiments,the method includes peptizing the highly dispersible alumina to form apeptized alumina and reacting the peptized alumina with precursors ofZrO₂, ZnO and CuO, as described above.

A highly dispersible alumina, as otherwise described herein, is preparedby adding the alumina to water to provide approximately 5 wt % to 35 wt% solids. The alumina and water mixture is mixed at high shear forapproximately one hour to form a slurry. In one or more embodiments, thealumina and water mixture is maintained at a pH in the range from about2 to about 5 during the mixing process at a temperature in the rangefrom about 20° C. to about 30° C. In a specific embodiment, the aluminaand water is maintained at a pH of about 3 during the mixing process. Inan even more specific embodiment, the temperature of the alumina andwater is maintained at about 25° C. The pH of the alumina and watermixture is maintained by adding an amount of acid to the mixture.Examples of suitable acids include nitric acid, formic acid, other knownacids and combinations thereof. As described herein, in one or moreembodiments the dispersible alumina may be replaced with nondispersiblealumina. For example, up to 99% of the dispersible alumina may bereplaced with nondispersible alumina that may include γ-alumina,η-alumina, χ-alumina, other transitional aluminas, boehmite,pseudoboehmite, gibbsite, bayerite, and mixtures thereof.

Prior to a first reaction of the peptized alumina and the ZrO₂precursor, the ZrO₂ precursor is prepared as a slurry in a separatevessel from the highly dispersible alumina. The process includesmaintaining the ZrO₂ precursor a low pH and a controlled temperature. Inone or more embodiments, the ZrO₂ precursor is maintained at a pH ofless than 2 or less than about 1.5. In one or more specific embodiments,the ZrO₂ precursor is maintained at a pH in the range from about 1.0 toabout 2.0. In a more specific embodiment, the ZrO₂ precursor ismaintained at a pH of about 1.0. The temperature of the ZrO₂ precursorof one or more embodiments is maintained at a temperature in the rangefrom about 20° C. to about 30° C. prior to the first reaction with thepeptized alumina. In one or more specific embodiments, the ZrO₂precursor is maintained at a temperature in the range from about 22° C.to about 28° C., or, more specifically, in the range from about 24° C.to about 26° C. In one variant, the ZrO₂ precursor is maintained at atemperature of about 25° C.

The dispersed alumina and water slurry is added to the slurry of theZrO₂ precursor and the alumina slurry and ZrO₂ precursor are well mixedfor a duration from about 30 minutes to about 60 minutes to form a firstreaction product, new slurry or mixed slurry. While the alumina slurryand the ZrO₂ precursor are mixed, the pH is maintained at less thanabout 1.5. In one or more embodiments, while the mixed slurry or firstreaction product is formed, the process includes maintaining the pH atabout 1 or as close to 1 as possible. The temperature is also maintainedat a range from about 20° C. and about 30° C. or, more specifically, at25° C.

In one or more embodiments, the CuO and ZnO precursors are preparedseparately for reaction with the first reaction product, new slurry ormixed slurry. In a separate vessel, a solution of the CuO precursor andZnO precursor is prepared to form a second reaction product. In one ormore specific embodiments, the second reaction product is provided byforming a solution of copper nitrate and zinc nitrate in a separatevessel. The temperature of second reaction product is maintained at atemperature in the range from about 30° C. to about 50° C. In one ormore specific embodiments the temperature of the second reaction productis maintained at about 40° C. In one variant, the pH of the secondreaction product is maintained at a pH of less than about 1.5 or, in amore specific variant, at about 1. In one or more specific embodiments,the second reaction product is maintained at this pH by the addition ofsoda ash, or other suitable sodium source, for example, sodiumhydroxide, sodium carbonate or sodium bicarbonate.

The second reaction product is then added to the first reaction productor mixed slurry. The first reaction product and the second reactionproduct are well mixed for a duration from about 30 minutes to about 60minutes. The temperature and/or pH may be adjusted or controlled tocreate an acidic slurry. The acidic slurry may containing coppernitrate, zinc nitrate, zirconyl nitrate and alumina.

In one or more embodiments, the first reaction product and the secondreaction product are maintained at a pH of less than about 1.5, or in amore specific embodiment, at about 1 or as close to about 1 as possible.The temperature may also be controlled. For example, in one variant, thetemperature of the first reaction product and the second reactionproduct is raised and maintained at a temperature in the range fromabout 30° C. to about 50° C. In one or more specific embodiments, thetemperature of the first reaction product and the second reactionproduct is raised and maintained at a temperature of about 40° C.

The acidic slurry formed from the first reaction product and the secondreaction product is then combined with a precipitation solution and aheel of water to form a precipitate slurry. The precipitation solutionmay include a basic solution of one or more of sodium carbonate andsodium bicarbonate and is formed separately from the heel of water. Theprecipitation solution may be formed at a temperature and/or have atemperature in the range from about 30° C. to about 50° C. or, in one ormore specific embodiments, a temperature of about 40° C. In one or moreembodiments, the slurry is formed by adding the acidic slurry and theprecipitate solution simultaneously and slowly to a separate vesselcontaining a heel of water to form a precipitate slurry. The heel ofwater may have a temperature in the range from about 30° C. to about 50°C. or, in one or more specific embodiments, a temperature of about 40°C. This simultaneous addition of the acidic slurry and the precipitationsolution improves the consistency in the precipitation of thecarbonates.

After addition, the first and second reaction products and theprecipitation solution are well stirred for a duration of about 90minutes. In one or more embodiments, precipitation reaction is performedor carried out at a pH that is controlled, for example, by adjusting theflow of the first and second reaction product and/or the flow of theprecipitation solution. In one or more embodiments, the pH is controlledto an amount in the range from about 6 to about 7 or, more specifically,in the range from about 6.5 to about 6.7. In one or more specificembodiments, the pH is controlled at about 6.5. The temperature of theprecipitation may be carried out at a temperature in the range fromabout 30° C. to about 50° C., or more specifically, a temperature ofabout 40° C.

In one or more embodiments, the precipitate slurry is digested or agedfor a duration of about 15 minutes to about 15 hours. In a specificembodiment, the precipitate slurry is digested or aged for a duration ofabout 1 hour to about 3 hours. In an even more specific embodiment, theprecipitate slurry is digested or aged for a duration of about 2 hours.The temperature of the precipitate slurry is increased to a temperaturein the range from about 30° C. to about 70° C. during aging or, morespecifically, to a temperature of about 60° C. In one variant, the pH ofthe precipitate slurry during digestion or aging is not controlled. Insuch embodiments, the pH of the precipitate slurry undergoes somechanges by cyclically increasing and decreasing, though the amount ofincrease and decrease may not be uniform. During the digestion or agingprocess, the color of the slurry changes from blue to green. In onevariant, the method includes filtering and washing the slurry to form afilter cake. The method may also include drying the filter cake to forma dry filter cake or dried powder. The dry filter cake or dried powdermay then be calcined to decompose any carbonates to oxides. In one ormore embodiments, the dry filter cake or dried powder may be calcinedfor a duration of about 2 hours at a temperature of about 350° C.

In one or more embodiments, the resulting catalyst, before reduction ofthe copper oxide to form copper metal, includes cupric oxide in anamount in the range from about 10% by weight to about 75% by weight. Inone variant, ZnO was present in the resulting catalyst, beforereduction, in an amount in the range from about 5% by weight to about70% by weight. In one or more embodiments, the catalyst includes ZrO₂ inan amount in the range from about 1% by weight to about 50% by weight,before reduction. In one or more embodiments, the catalyst includesalumina in an amount in the range from about 5% by weight to about 70%by weight, before reduction.

In one or embodiments, the prepared catalyst is further reduced. Avariant of the reducing step utilizes a hydrogen-containing gas.Specifically, such methods may include heating the catalyst to atemperature in the range from about 150° C. to about 200° C. whileflowing nitrogen gas at atmospheric pressure over the catalyst in areactor. In one or more specific embodiments, the catalyst is heated toa temperature in the range from about 165° C. to about 185° C. inflowing N₂. In a more specific embodiment, the catalyst is heated to atemperature of about 170° C. in flowing N₂. The nitrogen is replacedincrementally by hydrogen. The temperature may be slowly andincrementally increased to a maximum of about 220° C.

The resulting catalyst includes copper metal, formed form the reductionof the CuO precursor. The catalyst also includes ZrO₂, which functionsas a chemical promoter, while ZnO and alumina function as structuralpromoters. In one or more embodiments, at least the ZnO and ZrO₂ areclosely associated with the copper metal.

A third aspect of the present invention pertains to a method ofconverting alcohol to an ester or otherwise dehydrogenating an alcohol.One or more embodiments of the method include contacting analcohol-containing fluid stream with a catalyst as described herein anddehydrogenating the alcohol to an ester. The alcohol-containing fluidstream may be flowed at 1 h⁻¹ LHSV with a hydrogen-containing gas thatis flowed at 4.2 h⁻¹ GHSV. The catalyst utilized in the method toconvert alcohol may be reduced in a stream containing hydrogen. In oneor more embodiments, the alcohol may include ethanol and the ester thatis formed may include ethyl acetate.

Without intending to limit the invention in any manner, embodiments ofthe present invention will be more fully described by the followingexamples.

EXAMPLES

Two catalysts were prepared and the catalytic activity of each catalystwas measured. Both catalysts, Example 1 and Comparative Example 2,included CuO, ZnO, ZrO₂ and Al₂O₃. Example 1 was made with highlydispersible alumina having a dispersibility greater than about 90%,available under the trade name Catapal D from Sasol North America, Inc.Comparative Example 2 was made with aluminum nitrate. The components andquantities of the components used to make the final catalyst of Example1 and Comparative Example 2 catalyst in the oxide or unreduced form areprovided in Table 1.

TABLE 1 Amount, g Example 1 Reagents (solutions) 16% Copper in Nitratesolution 1919.6 16.5% Zinc in Nitrate solution 579.4 Al Nitrate solutionN/A 14.6% Zirconia in Nitrate 510.2 Al₂O₃ (@19% VF solids) 663.2 Waterto be added for dilution 2841.3 Sodium Carbonate 1146.7 Water 3631.1Total carbonate solution 4777.8 Water Heel 2124.6 Total wt of solution4461.6 Water in mix 1853.0 % total metal concentration in solution 25.3Water for required concentration 4694.3 Grams of metal in final catalystCu 307.1 Zn 95.6 Al from nitrate N/A Al from solid alumina 66.7 Zr 74.3Total g of metal 543.8 Comparative Example 2 Reagents (solutions) 16%Copper in Nitrate solution 1919.6 17% Zinc in Nitrate solution 562.47.2% Al in Nitrate solution 927.4 26.7% Zirconia in Nitrate 262.7 Al₂O₃(@19% VF solids) N/A Water to be added for dilution 2994.1 SodiumCarbonate 1146.7 Water 3631.1 Total carbonate solution 4777.8 Water Heel2124.6 Total wt of solution 3672.1 Water in mix 1700.2 % total metalconcentration in solution 27.6 Water for required concentration 4694.3Grams of metal in final catalyst Cu 307.1 Zn 95.6 Al from nitrate 66.7Al from solid alumina N/A Zr 52.0 Total g of metal 521.4

Example 1 is prepared according to the methods of preparing a catalystcomposition described herein. As Comparative Example 2 utilized aluminumnitrate as an alumina source and thus, did not contain any solidalumina. Accordingly, a different preparation procedure was utilized toform Comparative Example 2. Comparative Example 2 was formed usingcopper nitrate, zinc nitrate, zirconyl nitrate, and aluminum nitrateprecursors, which were all mixed together without the need for theinitial interaction of zirconyl nitrate with aluminum nitrate. Themixture had a pH of 2.5. A slurry was formed by precipitating themixture with soda ash at a pH of 7 and temperature of 60° C. The slurrywas then digested at a temperature of about 60° C. for a duration ofabout 90 minutes. The filtration, washing, drying, and calcination stepsfor preparing Comparative Example 2 were the same as for Example 1.Example 1 and Comparative Example 2 were reduced at approximately 210°C. using a gas containing 5% hydrogen in nitrogen, as described herein.Table 2 provides the analyses of Example 1 and Comparative Example 2before and after reduction.

TABLE 2 Analyses of Example 1 and Comparative Example 2 ComparativeExample Example 1 Example 2 Analyses % CuO 48.0 51.0 % ZnO 16.0 15.5 %ZrO2 12.1 11.5 % Al2O3 23.9 22.0 % Na2O 0.02 0.04 After reduction % Cu42.5 45.5 % rest of components as 57.5 54.5 oxides BET total surfacearea, m²/g 142 134

The Cu surface areas of reduced Example 1 and reduced ComparativeExample 2 as prepared in Example 1 were measured by a standard proceduredescribed by G. C. Chinchen et al. in Journal of Catalysis (1987), vol103, pages 79 to 86. After reducing, a reduced metallic Cu surface isobtained on both Example 1 and Comparative Example 2. A gas containing 2wt % N₂O in helium at a temperature of 60° C. is flow through reducedExample 1 and Comparative Example 2 for 10 minutes. It is believed thatthe nitrous oxide decomposes on the copper surface of the catalysts andthe resulting N₂ evolved is measured via a thermal conductivitydetector, while the oxygen atoms remain attached to the copper. Eachoxygen atom is attached to two surface Cu atoms. The amount of nitrogenevolved gives a measure of the number of number of oxygen atoms, andthus copper atoms available on the surface of the catalyst. The surfacearea of a Cu atom is 6.8×10⁻¹⁶ cm²/atom. By multiplying the number of Cuatoms by the area of each atom the copper surface area of the catalystis derived. The Cu dispersion, which is defined as surface copper atomsas a percentage of all copper atoms, and Cu surface areas of Example 1and Comparative Example 2 are shown in Table 3.

TABLE 3 Cu dispersion and Cu surface area Cu surface area, % Cudispersion m²/g of catalyst Example 1 10.4 28.4 Comparative 3.0 8.8Example 2

As is evident from Table 3, Example 1 made with dispersible alumina andwith the method described above exhibits a significant increase in theCu dispersion and surface area compared to Comparative Example 2, whichwas made with aluminum nitrate instead of a dispersible alumina.

A sample made in accordance with Example 1 was submitted for X-raydiffraction analysis using standard techniques. The sample was ground ina mortar and pestle. The resultant powder was then backpacked into aflat plate mount for use in reflection mode. X-ray diffraction wasperformed on a θ-θ PANalytical X′Pert Pro MPD X-ray diffractometer withCu_(kα) radiation. The generator settings were voltage 45 kV and current40 mA. The diffractometer optics utilized Bragg-Brentano geometry, a ¼°divergence slit, 0.04 radian soller slits, 15 mm beam mask and ½°anti-scatter slit. The data collection range was 8° to 80° two theta(2θ) using a step size of 0.0334° and counting for 240 seconds per step.As illustrated in FIG. 1, the catalyst exhibits an XRD patterncontaining boehmitic peaks at 2 theta values of about 14.2° and 28.1°.

As an example of the dehydrogenation catalysis of the catalystsdescribed herein, ethanol was reacted with Catalysts 1 and ComparativeExample 2, to form ethyl acetate. Before use Example 1 and ComparativeExample 2 were reduced in a hydrogen containing gas to obtain the finalcatalyst comprising of Cu, ZnO, ZrO₂, and Al₂O₃, as described herein.The catalyst reduction procedure utilized includes heating Example 1 andComparative Example 2 to a temperature of about 170° C. in 250 sccmflowing nitrogen gas at atmospheric pressure. Subsequently hydrogen isintroduced to the nitrogen flow in a step-wise fashion for up to about 1hour for each step, starting at low concentration as outlined below:

1. 12 cc/min H₂ in 238 cc/min N₂

2. 25 cc/min H₂ in 225 cc/min N₂

3. 50 cc/min H₂ in 200 cc/min N₂

4. 125 cc/min H₂ in 125 cc/min N₂

5. 200 cc/min H₂

Once reduction was completed, the temperature was increased to 220° C.in 200 sccm hydrogen, and then reactor was pressurized to 10 barsabsolute. Once temperature and pressure was stable, the ethanol feedstream was introduced to the reactor at 1 h⁻¹ LHSV (23.7 g/h) whilemaintaining hydrogen flow at 4.2 h⁻¹ GHSV (2 sccm).

To measure the catalytic activity of Example 1 and Comparative Example2, a stainless steel reactor tube having dimensions of approximately 84cm in length, 2.5 cm outer diameter and 2.1 cm inner diameter wasutilized. The reactor tube was equipped with a thermocouple well havingan outer diameter of 0.47 cm. The thermocouple well ran through thecenter of the tube and housed 5 thermocouples. The thermocouples werespaced evenly from the top to the bottom of the catalyst bed. Theaverage temperature of the thermocouples was used to controltemperature. Thirty cc of each of Example 1 and Comparative Example 2having a particle size in the range from about 30 mesh to about 50 meshwas mixed with 30 cc of interstitial packing for a total bed volume of60 cc. The interstitial packing included α-alumina granules having aparticle size in the range from about 28 to 48 mesh. The bed volumecorresponded to a reaction zone of about 18 cm length. α-aluminagranules having a particle size in the range from about 14 to about 28mesh was utilized as a preheat inert material and Denstone® 57 tabletsceramic bead support media having a length and width of 3 mm×3 mm wasutilized as a post catalyst inert material. The preheat zone was about35 cm long and the post catalyst zone was about 30 cm long. The reactorwas jacketed to accommodate a recirculating hot oil bath which heatedthe reactor, and ISCO Model 2350 HPLC pumps were used to pump a feedinto the reactor. The feed included a synthetic blend of 95% ethanol and5% isopropanol.

An on-line Agilent 6890 series gas chromatograph with DB-1701 capillarycolumn having dimensions 60 m×0.32 mm×1 μm, both available from AgilentTechnologies of Santa Clara, Calif., and an FID detector were utilizedto analyze the conversion of the feed. The heated lines to the gaschromatograph were maintained at a temperature in the range from about130° C. to about 150° C. The conversion, reaction rate and yield resultsof the feed using Example 1 and Comparative Example 2 are provided inTable 4.

TABLE 4 Reaction rate and yield results at constant conversion after 50hours reaction time on a feed stream at 220° C., 10 bars absolute, 1liquid hourly space-velocity. Reaction rate, % Ethanol mols ethanolEthyl acetate yield, conversion reacted/kg catalyst/h g/kg catalyst/hExample 1 25.7 23.1 957 Comparative 25.5 12.6 529 Example 2

Reference throughout this specification to “one embodiment,” “certainembodiments,” “one or more embodiments” or “an embodiment” means that aparticular feature, structure, material, or characteristic described inconnection with the embodiment is included in at least one embodiment ofthe invention. Thus, the appearances of the phrases such as “in one ormore embodiments,” “in certain embodiments,” “in one embodiment” or “inan embodiment” in various places throughout this specification are notnecessarily referring to the same embodiment of the invention.Furthermore, the particular features, structures, materials, orcharacteristics may be combined in any suitable manner in one or moreembodiments.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It will be apparent to those skilled in the art thatvarious modifications and variations can be made to the method andapparatus of the present invention without departing from the spirit andscope of the invention. Thus, it is intended that the present inventioninclude modifications and variations that are within the scope of theappended claims and their equivalents.

What is claimed is:
 1. A dehydrogenation catalyst comprising about 10 toabout 75 weight % CuO, about 5 to about 50 weight % ZnO, about 1 toabout 30 weight % ZrO₂, and about 5 to about 40 weight % aluminaprepared by peptizing dispersible alumina with a dispersibility of atleast about 50% or greater and reacting the alumina with precursors ofCuO, ZnO, and ZrO₂, wherein the dehydrogenation catalyst is effectivefor the dehydrogenation of alcohols.
 2. The catalyst of claim 1, whereinthe dispersible alumina has a dispersibility of at least about 70% orgreater.
 3. The catalyst of claim 1, wherein the dispersible alumina hasa dispersibility of at least about 90% or greater.
 4. The catalyst ofclaim 1, wherein the dispersible alumina is selected from boehmite,pseudoboehmite, and mixtures thereof.
 5. The catalyst of claim 1,wherein the catalyst exhibits an XRD pattern containing boehmitic peaksat 2 theta values of about 14.2° and 28.1°.
 6. The dehydrogenationcatalyst of claim 1, wherein the dehydrogenation catalyst comprises afirst reaction product of the alumina and a ZrO₂ precursor and a secondreaction product of CuO and ZnO precursors added to the first reactionproduct.